Greenlight Capital is suing Apple in federal court over attempts to eliminate preferred stock at the company. David Einhorn, who heads Greenlight, said the proposal would restrict the ability of Apple's board to unlock shareholder value. Some investors have been pushing Apple to do more with its enormous pile of cash -- $137 billion and growing.

When Warren Buffett announced in August that he would spend $5 billion to snap up Bank of America shares, investors cheered. Surely this must mean that we've seen the end of the bad news from America's biggest bank, right? Wrong. So did the Oracle of Omaha blunder?

The automaker's much-anticipated IPO includes plans to offer preferred stock in addition to the usual common stock. What's the difference between them, and which is a better investment? Here's a quick rundown.

Auto giant General Motors is expected to file for its IPO as soon as Wednesday. The filing is likely to include preferred as well as common shares and will help the government unload its 61% stake in the carmaker.